Preliminary Study Of Dispersive Clay With Calcium Bicarbonate Formed By Pseudo-karstification

Dispersive soil is a kind of cohesive soil that is dispersed and lost due to the repulsive force between the soil particles exceeding the attractive force under the condition of low hydraulic slope.Dispersible soil is a kind of water-sensitive soil,its erosion resistance is very low,and it is more sensitive to the water quality in the environment.In lower salt water or deionized water,the viscosity between the clay particles most or even all of the cohesion disappears,and the soil particles disperse themselves into primary cohesive soil particles.Due to the low anti-erosion ability of the dispersed soil,it is easy to cause pipeline accidents,caves and gully destruction in the project,which poses a great threat and hidden danger to the safety of the project.Therefore,it is necessary to modify the dispersed soil to improve the erosion resistance of the dispersed soil.In this paper,saturated calcium bicarbonate solution is used as a modified material.Through the physical property test,chemical property test,dispersibility identification test,scanning electron microscope test and energy spectrum analysis test of soil,the dispersion of calcium bicarbonate solution on dispersive soil.The effects of particle size,particle size,p H,conductivity of clarified solution and microstructure were analyzed.The mechanism of calcium bicarbonate modified dispersible soil was analyzed,and the feasibility and effectiveness of calcium bicarbonate modified dispersible soil were clarified.The conclusion of the study is as follows.(1)The conductivity test shows that as the pressure of carbon dioxide gas increases,the mass volume concentration of calcium bicarbonate in the prepared calcium bicarbonate solution increases,and calcium bicarbonate will slowly decompose to form calcium carbonate.After the calcium bicarbonate solution is mixed with the soil,the sedimentation speed of the soil particles increases significantly.The soil water suspension will produce obvious stratification in a short time.The upper solution is clear and transparent.There are almost no suspended clay particles in the solution,but there is still undecomposed calcium bicarbonate in the upper clear liquid.After the clarified liquid evaporates,scaly calcium carbonate crystals will form on the surface of the soil.Both methods of suction or filtration can increase the decomposition rate and conversion rate of calcium bicarbonate,and accelerate the precipitation and deposition of calcium carbonate.(2)The dispersibility identification test shows that calcium bicarbonate solution can effectively reduce the dispersibility of dispersible soil.The liquid-solid ratio and the soil-liquid separation method have an important influence on the modification effect.As the liquid-solid ratio increases,the dispersibility of the soil gradually decreases.When the liquid-solid ratio is 3:1,the dispersed soil turns into transitional soil;when the liquid-solid ratio is 4:1,the dispersed soil turns into Non-dispersed soil.The soil-liquid separation method of mixed suction filtration and air-drying has the characteristics of high decomposition rate of calcium bicarbonate,fast separation speed of soil-water suspension,and stable modification effect.(3)After the calcium bicarbonate solution is added to the dispersible soil,acid-base neutralization reaction,metathesis reaction,decomposition reaction and adsorption exchange reaction occur,which makes the soil p H lower and the thickness of the electric double layer between the soil particles decreases.Gelatinous calcium carbonate can play a role of cementation and solidification,forming larger agglomerates and improving the erosion resistance of the soil.These effects improve the bonding between the soil particles and enhance the structural stability of the soil.